This paper describes part of a systematic investigation aimed at producing more accurate theoretical models for internal combustion engine exhaust silencers. The performance of a number of silencer components, e.g. area discontinuities, branched systems, was measured in a very noisy exhaust system. These results were then compared with those predicted by the one-dimensional linearized theory with mean gas flow. It was found that this one-dimensional theory was sufficiently accurate for silencer design purposes.